Getting something close to the original finish is a combination of a good product and a good technique. Most find it helpful to do allot of practice of vertical panels (cardboard boxes will work in many cases) - of course with some of these products that may cost a bit but getting it right and not having to correct it later should be the goal.

What your going to need is first examples from the original car so that you can identify the original pattern and where it was applied, allot of the cars had some of the main floor pans coated also.

Products that seem popular when this subject comes up in recent years have been Lord Fusor and SecondSkin/Spectum Sludge. The later will need an top coat often to tint the final look correctly in areas where its not covered with body color (example rear wheel well and trunk)

Both will allow you to build the thickness up to 1/4" - up thickness and the sagging curtain look of some original examples

Lord Fusion comes in fairly small chalking tubes while Sludge can be purchased in a 1 gallon tub, its two part

If you do a search you'll find pictures, opinions and experiences from members in past threads. Let us know if we can help more.